Lighting-emitting diode (LED) is a solid state light emitting element. By applying a positive voltage to a semiconductor chip to create an electroluminescent effect, the monochromatic and discrete light can be generated. At the beginning, the LED was mostly used for signal light or display panels. With advance of technology on white light LED, now it can also be used on illumination. Incorporated with technology progress of material and manufacturing process, now the LED can compete with conventional lighting devices (such as incandescent lamps, fluorescent lamps, cold cathode fluorescent lamps and the like), and increasingly displaces them in many applications.
In the conventional LED technologies, such as U.S. Pat. No. 6,975,513 and U.S. patent application No. 20070228387, a light emitting chip is soldered on a heat dissipating base. In addition to holding the light emitting chip in a contact manner, the heat dissipating base also disperses heat generated by the light emitting chip. The bonded chip and base have to go through a packaging process to protect the chip and conductive wires connecting externally. The package material generally is transparent such as Epoxy or Silicone gel. It has to meet bonding and light penetration requirements, and also has to be solidified easily to form a curved surface to control light radiation direction and angle. However, the package material and heat dissipating base are two different types of materials with different characteristics, their contact surfaces are parallel, hence the package material and the base are separated easily and result in package defects. In serious conditions, the chip could be damaged and product yield drops.
U.S. Pat. Nos. 6,943,433 and 6,501,156 also provide other package techniques that have a heat dissipating base with a boss formed thereon to bond package material. The boss is formed in one direction on the heat dissipating base. While it can harness the package material from separating the heat dissipating base, it does not provide turning resistance of the package material relative to the base when a torsional force is applied. As the chip and conductive wires are fixedly held in the package material, in the event that a relative turning occurs to the package material and base, the structure of the chip and conductive wires could be damaged and also result in product defects.